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Old 06-04-2002, 04:22 PM
JCE's Avatar
JCE JCE is offline
Down to the Wear Bars
Join Date: May 1999
Location: So Kalifornia
Posts: 2,189
I converted over to r134a several years back, as I had an AC leak and r12 wasn't legally available in my county in SoCal. It seems to cool as much as I want on even 95 degree/80% humidity days. However, it also seems to take a little longer to get the temp down than did the r12. All in all, no complaints so far.

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

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Old 06-05-2002, 10:57 AM
edblock's Avatar
Registered User
Join Date: Sep 2001
Location: Austin, TX
Posts: 55
Unhappy A/C woes...(long story)

I live near Austin, TX. I have no A/C, despite spending upwards of $500 and several hours of greasy cursing. Here is my saga.

I purchased my 1978 300SD (W116) in February. I got it for $2,500 and it had only 97,000 actual miles. The car runs and drives great. When I bought it, I noticed that the A/C belt had been removed, so I figured there was a problem there.

Upon further inspection, the compressor turned easily with a socket/ratchet on the shaft nut, and depressing the low-side Schrader valve with a small screwdriver produced pressure and very light blonde colored oil. Main problem I saw was that the electrical connector on the clutch (where the power wires plug in) was broken off. Since a new clutch was only $30 cheaper that a whole new compressor, I decided that it would be worth the time and expense to replace what appeared to be the original R4 compressor with a new one with new clutch. So, I ordered compressor (new, not rebuilt), dryer, pressure and temp switches, and expansion valve--about $350. While waiting for the parts to arrive, I took the online test to get EPA 609 certification so I could legally purchase R-12.

When the new parts came, I followed the directions to the letter: I took the old parts off, flushed the lines and condenser with brake cleaner and compressed air, added the proper amount of mineral oil, and reassembled with the new parts. My neighbor is an A/C tech for Fox company, so I borrowed his gauges and vacuum pump. I pulled a vacuum for 1.5 hours then turned off the pump; it held 30 in Hg for 20 minutes so I figured all is well. I purchased 3 cans of R-12 and the can tap/hose assembly, about $120 total. I charged the system and it cooled, with pressures within correct range. I left it idling, removed the gauges, and walked across the street to return tools to my neighbor--for about 20 minutes...then the brand-new compressor locked up.

My parts vendor ( said that he would warranty the compressor, drier, and expansion valve even though it probably failed due to inadequate flushing. He sent out new parts and I started over. I decided that I couldn't afford another round of R-12, so I would make the switch to R-134a. I flushed, and flushed, and flushed and flushed...condensor, evaporator, all lines, in both directions--first using brake cleaner and then the special flush juice that costs $12 a quart. Added oil, reassembled, pulled vacuum, charged with R-134a according to the directions. It cooled 25-30 degrees below ambient temp so I thought all was well again.

It lasted about three days, then it quit cooling as well and the compressor clutch began slipping. I gave up and took it to a shop for diagnosis. They told me that the oil was black and the compressor was shot--probably a blockage in the condensor. I don't want to ask Rusty to send me another new compressor, so I'll just have to wait until I can afford another $500 to fix it AGAIN.
1978 300SD 149K miles silver-blue "Maxine" (mine!)
1979 300SD 318K miles red "Helga" (SOLD)
1980 300SD 321K miles yellow "Linda" (younger daughter's)
1980 300SD 148K miles blue (SOLD)
1980 300SD 153K miles green(parts car, SOLD)
Yes, I have a W116 fetish :-)
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